(i) Botulism Information Note on Bovine for Vets and Farmers

Botulism is an intoxication that is usually associated with the ingestion of neurotoxin contaminated food. There are 7 serologically distinct forms of the neurotoxin, types A, B, C1, D, E, F and G and they have similar pharmacological activity. Types A, B, E and rarely F can affect humans. Types C and D are more commonly associated with animal disease and generally humans appear to be refractory to these serotypes.

Type C and D C. botulinum are obligate parasites requiring decomposing carcasses for multiplication and toxin production. Although Type B Clostridium botulinum is common in Irish soil, there have been no recorded cases in Ireland. Type B outbreaks in cattle have been reported in Holland and the USA which is usually associated with poorly conserved forage.

In the Irish outbreaks associated with poultry litter Types D or rarely C toxin have been identified. This is significant in that Types D and C Cl. Botulinum will only grow and produce toxin on rotting carrion or vegetation. Even small pieces of carcass or a dead rodent are enough to contaminate a silage pit. Therefore when looking at control at farm level one must look at the factors that influence spread of the toxin in the farm i.e. carcasses, maggots, scavengers, litter, waste water from poultry houses etc. In addition the provision of advice, regarding the measures to be adopted with a view to reducing the risk of disease occurring e.g. the risk associated with the spreading of poultry litter and the steps to be taken in the event of a suspect outbreak, is important.

Clinical Signs:

Clinical signs are variable. Peracute cases may appear as 'sudden deaths'. Signs of flaccid paralysis begin 24 hours to 7 days after ingestion. A progressive paralysis usually begins with posterior ataxia (similar to 'milk fever') progressing to the forequarters and head. Some of the following signs may be observed in animals; knuckling, stiffness in the hindquarters, tongue paralysis, drooling, rumen stasis, bloat, diarrhoea, constipation, papillary dilation and sweating. Affected animals lie down and rapidly dehydrate. They generally appear bright. Death may occur within 24 hours to several weeks. Rarely there is recovery.

Laboratory Confirmation:

Laboratory confirmation is difficult to achieve however it is important that attempts are made to isolate toxin, contact should be made by the herdowners private veterinary practitioner with the nearest Regional Veterinary Laboratory with regard to the outbreak. There are no pathognomonic necropsy lesions associated with botulism in the cow.

Treatment:

There is no practical treatment in the bovine. Euthanasia is indicated on welfare grounds if the animal is distressed. In early mild cases a purgative may be beneficial along with supportive therapy. Do not treat with procaine penicillin, tetracyclines or amino glycosides as these drugs may accentuate clinical signs of neuromuscular blockade.

Prevention:

There is no vaccine licensed in Europe for botulism. Control measures are described in the attached documents:

Further advice may be sought from your Regional Veterinary Laboratory, or your local District Veterinary Office or, the Central Veterinary Research Laboratory at (01) 6157100.

Public Health:

It is generally accepted that humans are refractory to types C and D botulism. The risk to human health from consumption of meat or milk of healthy animals from farms where botulism has occurred appears to be negligible.[1]

Reporting:

Botulism in the bovine is not a notifiable disease. However it is essential that all suspect cases of botulism are reported in order that the incidence and extent of outbreaks are monitored and that samples can be obtained and analysed in an attempt to identify the toxin.

Suspect cases should be reported by the herdowner's private veterinary practitioner to the Regional Veterinary Research Laboratory and to the local District Veterinary Office.